The sulfonylurea herbicides are an extremely potent class of herbicides discovered relatively recently which generally consist of a sulfonylurea bridge, --SO.sub.2 NHCONH--, linking two aromatic or heteroaromatic rings. Such herbicides have become commercially important. There is, therefore, a continuing need to discover new processes for their preparation that offer advantages that add to their commercial desirability.
WO 89/01937 generically discloses, in part, certain compounds of Formula I as intermediates to pyridine sulfonylureas.
U.S. Ser. No. 07/666,109 discloses the preparation of methyl 1,2-dihydro-2-oxo-6-(trifluoromethyl)-3-pyridinecarboxylate and methyl 2-bromo-6-(trifluoromethyl)-3-pyridinecarboxylate.
Lang, R. W. and Wenk, P.F., Helvetica Chimica Acta, 1988, 71, 599-601 also teaches the preparation of ethyl 1,2-dihydro-2-oxo-6-(trifluoromethyl)-3-pyridinecarboxylate.